Having started to listen to barbos' second Mearsheimer video, I confess that it doesn't strike me as really relevant to the topic of this thread--the Ukraine situation. Rather, it is a more general lecture on Mearsheimer's view of the evils of "liberal hegemony", which he tends to equate with US foreign policy. He starts out with very nice definitions of "liberalism" and "nationalism", which are two different ways to see world politics, and then he launches into his ideas about where the US goes wrong in pursuing its so-called liberal hegemony. The discussion is quite interesting, but not really relevant to the topic here. So I don't intend to comment further on the Bucharest lecture, although I may continue watching it for my own edification. Mearsheimer isn't a bad speaker, and he is promoting a book that he had just published. I still think he goes astray by treating most countries outside of liberal democracies as if liberal democracy did not matter to the citizens of those countries. Rather he tends to see it as something that the US and other democracies are responsible for promoting. IOW, all of those popular uprisings against authoritarian regimes are caused by US meddling, not globalization. In fact, I am curious to see what, if anything, he has to say about the globalization of economies, since he seems to realize that authoritarian leaders depend on liberal democracies as a safe haven for their private wealth. It is certainly something that matters to a lot of Russians, and that is why Putin faces a lot of popular opposition these days. He is trying to promote nationalism over liberalism as the correct perspective to take on current events.
ETA: An interesting fact about Mearscheimer is that he is not a conservative Trump-supporting American. Nor is he some kind of Putin apologist, although I'm sure that he has been accused of that. He is a liberal-progressive Democrat who has supported Bernie Sanders in the past. Had Sanders managed to become President, Mearscheimer could possibly have become part of the Sanders administration and played a role in shaping US foreign policy. He would be deeply opposed to Biden's foreign policy, which he would equate with liberal hegemony.